When applied to various adherends, pressure-sensitive adhesive tapes or sheets must readily and firmly adhere to predetermined positions of the adherends. For this purpose, pressure-sensitive adhesive tapes or sheets are required to have good reworkability (they can be temporarily fixed on adherends and can be re-attached to them) and good repositionability (they can be re-positioned on adherends). For example, regarding the operation of applying a pressure-sensitive adhesive tape or sheet to a predetermined site, there is mentioned one example of adhering a flooring material to a floor base. In the operation of adhering a flooring material to a floor base, the flooring material must be inserted into a predetermined area on a floor base. For this purpose, the flooring material, after having been inserted into a predetermined area on a floor base, must be moved for a relatively long distance along the floor base. In this operation, when a pressure-sensitive adhesive tape or sheet having a pressure-sensitive adhesive layer of an ordinary pressure-sensitive adhesive is used, then the flooring material could not be moved along the floor base after it has been inserted into a predetermined area on it, because of the tackiness and the initial adhesiveness of the pressure-sensitive adhesive. To solve the problem, various methods have been proposed. One comprises using a pressure-sensitive adhesive tape or sheet of which the pressure-sensitive adhesive force is temporarily lowered by the use of water or an organic solvent, or comprises disposing water-swollen granules of a water-absorbing polymer in the interface between the surface of a pressure-sensitive adhesive layer and an adherend (see Patent Reference 1); another comprises using a pressure-sensitive adhesive tape or sheet of which the pressure-sensitive adhesive layer is specifically so designed that its surface has an uneven structure to thereby lower the initial adhesive area thereof (see Patent Reference 2); and still another comprises using a pressure-sensitive adhesive tape or sheet of which the pressure-sensitive adhesive layer is spotted with projections of a non-tacky solid substance to thereby control the initial adhesive force thereof (see Patent Reference 3).
[Patent Reference 1]Japanese Patent No. 3296769[Patent Reference 2]JP-A-2002-121503[Patent Reference 3]JP-A-7-310057
In the method of disposing water-swollen granules of a water-absorbing polymer in the interface between the surface of a pressure-sensitive adhesive layer and an adherend, for example, as in Japanese Patent No. 3296769, water is used. However, since water essentially retards adhesion, and using it is undesirable in view of the reliability of adhesion.
In the method of using a pressure-sensitive adhesive tape or sheet of which the pressure-sensitive adhesive layer is specifically so designed that its surface has an uneven structure to thereby lower the initial adhesive area thereof, for example, as in JP-A-2002-121503 (The term “JP-A” as used herein means an “unexamined published Japanese patent application”), the surface of the pressure-sensitive adhesive tape or sheet has a pressure-sensitive adhesive layer existing thereon. In the method, therefore, the width of the correctable position from the temporarily-fixed position is limited, and the repositionability of the pressure-sensitive adhesive tape or sheet is unsatisfactory.
In the method of using a pressure-sensitive adhesive tape or sheet of which the pressure-sensitive adhesive layer is spotted with projections of a non-tacky solid substance to thereby control the initial adhesive force thereof, for example, as in JP-A-7-310057, the non-tacky substance is merely attached to the surface of the pressure-sensitive adhesive layer and its structure is not controlled. Therefore, for making the pressure-sensitive adhesive tape or sheet exhibit good repositionability, the amount of the non-tacky substance to be applied thereto inevitably increases, which, however, is undesirable in view of the pressure-sensitive adhesion characteristics of the tape or sheet.